add fs providers hook

Signed-off-by: Nicola Murino <nicola.murino@gmail.com>

internal/vfs/filesystem.go

@@ -16,10 +16,17 @@ package vfs
 
 import (
 	"os"
+	"slices"
 
 	"github.com/sftpgo/sdk"
 
 	"github.com/drakkan/sftpgo/v2/internal/kms"
+	"github.com/drakkan/sftpgo/v2/internal/util"
+)
+
+var (
+	disabledFilesystemProviders []sdk.FilesystemProvider
+	loadDisabledProvidersFn     func()
 )
 
 // Filesystem defines filesystem details
@@ -232,8 +239,7 @@ func (f *Filesystem) Validate(additionalData string) error {
 		f.CryptConfig = CryptFsConfig{}
 		f.SFTPConfig = SFTPFsConfig{}
 		return nil
-	default:
-		f.Provider = sdk.LocalFilesystemProvider
+	case sdk.LocalFilesystemProvider:
 		f.S3Config = S3FsConfig{}
 		f.GCSConfig = GCSFsConfig{}
 		f.AzBlobConfig = AzBlobFsConfig{}
@@ -241,6 +247,11 @@ func (f *Filesystem) Validate(additionalData string) error {
 		f.SFTPConfig = SFTPFsConfig{}
 		f.HTTPConfig = HTTPFsConfig{}
 		return validateOSFsConfig(&f.OSConfig)
+	default:
+		return util.NewI18nError(
+			util.NewValidationError("invalid filesystem provider"),
+			util.I18nErrorFsValidation,
+		)
 	}
 }
 
@@ -390,3 +401,11 @@ func (f *Filesystem) GetACopy() Filesystem {
 	}
 	return fs
 }
+
+// IsFsDisabled returns if a filesystem provider is disabled
+func IsFsDisabled(provider sdk.FilesystemProvider) bool {
+	if loadDisabledProvidersFn != nil {
+		loadDisabledProvidersFn()
+	}
+	return slices.Contains(disabledFilesystemProviders, provider)
+}

internal/vfs/folder.go

@@ -140,6 +140,9 @@ type VirtualFolder struct {
 
 // GetFilesystem returns the filesystem for this folder
 func (v *VirtualFolder) GetFilesystem(connectionID string, forbiddenSelfUsers []string) (Fs, error) {
+	if IsFsDisabled(v.FsConfig.Provider) {
+		return nil, fmt.Errorf("filesystem provider %d is disabled", v.FsConfig.Provider)
+	}
 	switch v.FsConfig.Provider {
 	case sdk.S3FilesystemProvider:
 		return NewS3Fs(connectionID, v.MappedPath, v.VirtualPath, v.FsConfig.S3Config)